Jason Statham turned 50 last year, and while he's still in tremendous shape, he's no longer young or obscure enough to toil away in B-movies, nor is he quite of the disposition to sign up for superhero duty. Maybe it's only natural that he would pit himself against a special effect, as he does in this week's The Meg, a long-gestating adaptation of a pulp novel about an unearthed prehistoric shark.

Though far from prehistoric, Statham came to movie stardom a little late, after shoring up his physical bona fides as a diver for Britain's national team in the early '90s. He eventually worked his way into satisfying B-pictures like the Transporter trilogy and the Crank films, accruing enough fan cred to get hired into all-star crews for both The Expendables and the later Fast and Furious movies. Statham has a spin-off of the latter series set for next year with Dwayne Johnson, and it will almost certainly be his biggest hit in a starring role.

But outside of cog work in franchises, it's not always easy for an industry that's trying to abandon mid-budget action movies to figure out a place for someone like Jason Statham. Hence the shark.

Acting opposite a CG shark is not necessarily a bad career move. A couple of summers ago, Blake Lively gave one of her best performances in The Shallows, doing a de facto solo act as a young woman trapped on some rocks while a malevolent beast circled. The filmmakers behind The Meg may not have seen The Shallows, and are adapting a book that's been around for 20 years, but when a whale carcass figures into the plot, it's easy to wonder if the bigger (but vaguely cheaper-looking) movie is ripping off the smaller one.

In general, The Meg is more akin to Deep Blue Sea in enthusiastic silliness. It supposes that the Mariana Trench is far deeper than previously imagined, and that Jonas Taylor (Statham) is relatively unsurprised to see a prehistoric megalodon emerge from it, his past suspicions of its existence dismissed as "pressure-induced psychosis." Statham is the kind of actor who makes boilerplate backstory — a rescue mission that went wrong; an old flame whose endangerment will spur him back into action — charming just by playing it straight with a hint of self-awareness.

He turns out to be a better effect than the giant shark, mostly because director Jon Turteltaub, a longtime hand at live-action Disney movies, doesn't have the ruthlessness required to goose either the suspense or the mayhem of a giant-shark movie. When he initially cuts around the full presence of the shark, in faux-Jaws fashion, he just winds up making the creature's early attacks look confusing. Later set pieces feel rushed and perfunctory, as if he's desperate to find his way out of them as soon as possible, and he only intermittently gets a handle on the sheer scale of the creature. This isn't a Disney movie, but it makes bizarre feints toward family-friendliness, resulting in a shark movie with a frustratingly low body count. Statham's Frank Martin from the Transporter series has probably killed more people than this megalodon.

The Meg has its dumb-fun pleasures. Statham does go after the giant shark in that unwavering way that makes it all seem like a surprisingly fair fight. It's neat to see him in the water, winking (intentionally or not) at his history as a diver, and it's downright delightful to hear him quoting Finding Nemo. It's not that the Transporter movies are so much more sophisticated than this one. But the best Jason Statham vehicles and the best silly monster movies tend to understand that they are dealing at least in part with pulpy wish fulfillment: What if a group of giant sharks got super-smart and turned on humans? What if Jason Statham had to fight a garage full of goons using only his wits, muscles, and a drum of oil?

The Meg kinda-sorta explains what would happen if Jason Statham fought a giant shark. But mostly it asks and answers a different and more familiar question: What happens when a B-movie gets too big?